Wing Cheung Wong

Anatomic variations of neurovascular structures of the ankle in relation to arthroscopic portals: a cadaveric study of Chinese subjects.

Purpose. To investigate anatomic variations of neurovascular structures in the ankle and the safety margin for arthroscopic portals. Methods. 11 left and 12 right ankles from 8 female and 15 male fresh cadavers of Chinese ethnicity aged 53 to 88 (mean, 68) years were used. The ankle was standardised in a plantigrade position, zero-degree inversion, and neutral rotation. Four ankle portals, namely anteromedial (AM), anterolateral (AL), posteromedial (PM) and posterolateral (PL), were identified using 23-gauge needles. Skin and subcutaneous fat were dissected from the underlying fascia to visualise neurovascular structures. Distances were measured from: (1) the AM portal to the saphenous vein and nerve and its branches, (2) the AL portal to branches of the superficial peroneal nerves, of which the lateral one was labelled as the intermediate dorsal cutaneous branch and the medial one as the medial dorsal cutaneous branch, (3) the PM portal to the posterior tibial neurovascular bundles, and (4) the PL portal to the sural nerve. Results. The distances from (1) the AM portal to branches of the great saphenous vein and nerve, and (2) the AL portal to the intermediate dorsal cutaneous branch of the superficial peroneal nerve were short and may be an anatomic hazard. Variations were significant among the cadavers in terms of distances of the portals to the neurovascular structures. Conclusion. In Chinese cadavers, variations of neurovascular structures are significant. Care must be taken to avoid inadvertent injury during ankle arthroscopy.

Spatial analysis of falls in an urban community of Hong Kong

BackgroundFalls are an issue of great public health concern. This study focuses on outdoor falls within an urban community in Hong Kong. Urban environmental hazards are often place-specific and dependent upon the built features, landscape characteristics, and habitual activities. Therefore, falls must be examined with respect to local situations.ResultsThis paper uses spatial analysis methods to map fall occurrences and examine possible environmental attributes of falls in an urban community of Hong Kong. The Nearest neighbour hierarchical (Nnh) and Standard Deviational Ellipse (SDE) techniques can offer additional insights about the circumstances and environmental factors that contribute to falls. The results affirm the multi-factorial nature of falls at specific locations and for selected groups of the population.ConclusionThe techniques to detect hot spots of falls yield meaningful results that enable the identification of high risk locations. The combined use of descriptive and spatial analyses can be beneficial to policy makers because different preventive measures can be devised based on the types of environmental risk factors identified. The analyses are also important preludes to establishing research hypotheses for more focused studies.

Anterior spinal fusion versus laminoplasty for cervical spondylotic myelopathy: a retrospective review

Purpose. To compare outcomes of anterior spinal fusion (ASF) versus laminoplasty for cervical spondylotic myelopathy (CSM). Methods. Records of 26 women and 37 men aged 34 to 83 (mean, 67) years who underwent ASF or laminoplasty for CSM were reviewed. Patient demographics, duration of symptoms, pre- and postoperative Japanese Orthopaedic Association (JOA) scores, Hirabayashi recovery rate, and radiographic features (including anteroposterior canal diameter, Pavlov ratio, and number of levels compressed) were compared. Results. The mean duration of symptoms was 9 months. The mean follow-up period was 40 months. Patients who underwent laminoplasty were older (p=0.015) and had more levels compressed (p<0.001) than those who underwent ASF. Patients with C3/4 compression were older than those without it (p=0.044). Younger patients had higher Hirabayashi recovery rate (p=0.043). Conclusion. The surgical decision for ASF or laminoplasty mainly depends on the number of levels compressed and patient age. Laminoplasty is usually reserved for older patients with multiple-level involvement. Age is the main predictive factor for surgical outcome.

A Small-Area Study of Environmental Risk Assessment of Outdoor Falls

Falls in public places are an issue of great health concern especially for the elderly. Falls among the elderly is also a major health burden in many countries. This study describes a spatial approach to assess environmental causes of outdoor falls using a small urban community in Hong Kong as an example. The method involves collecting data on fall occurrences and mapping their geographic positions to examine circumstances and environmental evidence that contribute to falls. High risk locations or hot spots of falls are identified on the bases of spatial proximity and concentration of falls within a threshold distance by means of kernel smoothing and standard deviational ellipses. This method of geographic aggregation of individual fall incidents for a small-area study yields hot spots of manageable sizes. The spatial clustering approach is effective in two ways. Firstly, it allows visualisation and isolation of fall hot spots to draw focus. Secondly and especially under conditions of resource decline, policy makers are able to target specific locations to examine the underlying causal mechanisms and strategise effective response and preventive measures based on the types of environmental risk factors identified.

Single-Door Cervical Laminoplasty Using Titanium Miniplates Alone

Purpose. To review outcome of 29 patients who underwent single-door cervical laminoplasty for myelopathy using titanium miniplates alone. Methods. Records of 20 men and 9 women aged 35 to 79 (mean, 64.3) years who underwent single-door cervical laminoplasty for myelopathy using titanium miniplates alone were reviewed. A total of 125 laminae were opened; 97 of them were fixed with a titanium miniplate. In 19 patients, a 20-hole titanium miniplate bent to the contour of a lamina was used and fixed into 3 laminae at alternate levels. In the remaining 10 patients, the pre-contoured ARCH Laminoplasty System was used and fixed into all laminae. In most patients, screw fixation was unicortical, and no spacer or bone graft was used. Results. The mean follow-up duration was 4 (range, 2–9) years. At one-year follow-up, the mean Japanese Orthopaedic Association (JOA) score improved from 9.2 to 13.2 (p<0.001). The mean JOA recovery rate was 64%. No patient had neurological deterioration. The mean anteroposterior diameter increased from 14.3 mm to 19.7 mm; the mean increase was 6.1 mm in the plated laminae and 5.3 mm in the unplated laminae (p=0.11). Out of the 125 laminae, there were 2 hinge non-unions in the unplated laminae, and 2 screw pullouts (not associated with plate loosening). No patient had penetration into the vertebral foramen or neuroforamen. Spring-back closure occurred in 5 (18%) of the 28 unplated laminae, with a mean of <3 mm loss of the initial expansion. Two patients developed transient C5 palsy presenting as shoulder abduction weakness. One patient had a delayed dural tear due to a sharp spike at the edge of the opened C6 lamina. Conclusion. Single-door cervical laminoplasty using miniplates alone is a safe technique and achieves a high hinge union rate, good canal expansion, and neurological recovery.

Rotary subluxation of the metacarpophalangeal thumb joint: a case report

Irreducible rotary subluxation of the metacarpophalangeal joint (MCPJ) of the thumb is a rare entity. Open reduction is indicated when signs of irreducibility are seen on the radiographs. We present one such case caused by displacement of the sesamoid bone into the intercondylar notch of the first metacarpal bone. A 35-year-old woman sustained a twisting injury to her right thumb by pronating and hyperextending it while attempting to retrieve things that she had dropped into a basin conduit. True lateral radiographs showed rotary subluxation of the thumb MCPJ, a sesamoid bone overlapping with the metacarpal head, and loss of the subsesamoid joint space and an incongruent MCPJ on full flexion. A high level of clinical suspicion is needed to diagnose this rare entity.

Quantitative Anatomy of C7 Vertebra in Southern Chinese for Insertion of Lateral Mass Screws and Pedicle Screws

Study Design Retrospective study. Purpose To analyze the quantitative anatomy of C7 vertebra for insertion of lateral mass screws and pedicle screws in Southern Chinese patients. Overview of Literature C7 lateral mass is smaller when compared to other subaxial cervical levels, which limits the length of lateral mass screws that can be used. Some studies have suggested pedicle screws for better fixation. But, this option is limited by the narrow pedicle width. Methods We have obtained computed tomography (CT) cervical spine data in 0.625 mm slices from our radiology department. The patients were adults. CTs were from May to August, 2015. The lateral mass screw length was measured using Margerls technique and pedicle width and pedicle screw trajectory were determined in three-dimensional reformated images. Results CT scans of cervical spines of 94 patients were obtained and 188 lateral masses and pedicles of C7 vertebrae were measured. The mean lateral mass screw length was 13.2 mm (standard deviation [SD] 1.6 mm), mean outer pedicle width was 5.9 mm (SD 1.0 mm) and mean pedicle screw trajectory was 29.4 degrees (SD 3.6 degrees). Most (91.0%) of the pedicles had an outer diameter ≥4.5 mm. Conclusions The mean lateral mass screw length was longer when compared with other similar studies, while the mean outer pedicle width was narrower. Nearly 10% of the pedicles were unable to accommodate 3.5 mm screws. These findings favor the use of lateral mass screws to provide a safe and stable fixation for C7 vertebrae in Southern Chinese patients, while the final choice of fixation method should only be confirmed after careful preoperative planning with CT scan.

Magnetic Resonance Imaging of the Subcoracoid Region and Its Relationship with Subscapularis Lesions in the Chinese Population: 在中國人群組中用磁力共振來評估下喙突區域及其與肩胛下肌病變的關係

Introduction: Coracoid impingement is considered a known yet frequently overlooked cause of anterior shoulder pain. Subcoracoid stenosis has been shown to be related to subscapularis tear. Studies have shown that patients with coracoid impingement have a shorter coracohumeral distance (CHD) and a larger coracoid overlap (CO) but these are based on data from Western populations. The aim of our study was to provide a local database on the MRI measurement of these parameters in our Chinese population and raise the awareness of this disease entity. Methods: All the shoulder MRI films taken in our hospital in 2011 were retrospectively reviewed and classified into two cohorts. The control group consisted of patients who had no subscapularis lesion. The subscapularis lesion group consisted of patients with complete tear, partial tear or abnormal signal over the subscapularis tendon. The CHD and CO were measured. Results: We reviewed 133 sets of shoulder MRI obtained in our hospital during 2011. Thirteen patients were noted to have subscapularis lesion. The CHD in the subscapularis lesion group was 6.24 ± 2.18 mm. The CHD in the control group was 9.95 ± 3.9 mm. Women had shorter CHD (8.18 ± 2.57 mm) than men (11.0 ± 4.54 mm). We failed to notice any statistically significant difference with regards to CO, coracoid process and lesser tuberosity morphology between the two groups of patients. Conclusion: MRI assessment of CHD can be useful in identifying patients at risk of having subscapularis lesion and coracoids impingement.

The Inaccuracy of Surface Landmarks for the Anterior Approach to the Cervical Spine in Southern Chinese Patients

Study Design Observational study. Purpose To assess the correlational accuracy between the traditional anatomic landmarks of the neck and their corresponding vertebral levels in Southern Chinese patients. Overview of Literature Recent studies have demonstrated discrepancies between traditional anatomic landmarks of the neck and their corresponding cervical vertebra. Methods The center of the body of the hyoid bone, the upper limit of the lamina of the thyroid cartilage, and the lower limit of the cricoid cartilage were selected as representative surface landmarks for this investigation. The corresponding vertebral levels in 78 patients were assessed using computed tomography. Results In both male and female patients, almost none of the anatomical landmarks demonstrated greater than 50% correlation with any vertebral level. The most commonly corresponding vertebra of the hyoid bone, the lamina of the thyroid cartilage, and the cricoid cartilage were the C4 (47.5%), C5 (35.9%), and C7 (42.3%), respectively, which were all different from the classic descriptions in textbooks. The vertebral levels corresponding with the thyroid and cricoid cartilage were significantly different between genders. Conclusions The surface landmarks of the neck were not accurate enough to be used as the sole determinant of vertebral levels or incision sites. Intra-operative fluoroscopy is necessary to accurately locate each of the cervical vertebral levels.

Are the Current Size Options of Glenoid Baseplates for Reverse Shoulder Arthroplasty Sufficient for our Local Population?: 現有反置式人工肩關節置換術中盂底板組件的大小選項是否滿足我們本地人口的需要？

Background/Purpose Reverse shoulder arthroplasty (RSA) is an effective treatment for patients who suffer from shoulder pain and dysfunction associated with a variety of shoulder pathologies including severe rotator cuff deficiency with or without glenohumeral arthritis. It has been widely used in European countries and the United States and is now gaining popularity in Asia, including Hong Kong. However, there are only limited size options available for glenoid baseplates, with 25 mm being the smallest size in some commonly used systems. The aim of our study is to perform computerized tomography (CT) measurements of the glenoid dimension in the Chinese population and to see if the current glenoid baseplate component size option is sufficient for our local population. Methods A total of 70 CT scans of shoulder regions were analysed. Measurements included maximum superoinferior height and the anteroposterior height. Results The glenoid dimensions were smaller compared to those from previous studies in Caucasian counterparts. Some 41% of female glenoids had widths measuring < 25 mm (25 mm being the smallest size available in some commonly used RSA systems). Conclusion Although there are only limited size options available for the glenoid baseplate in RSA, from our data, it should be able to cover most patients in our local population. However, surgeons should exercise special care when contemplating performing reverse shoulder replacement for small size females in our local population.